The invention relates to a method for preparing a concentrated coffee extract (hereinafter: coffee concentrate), and to the extract or concentrate to be obtained therewith. In this description and in the claims, the wording “coffee concentrate” indicates a concentrated coffee extract, irrespective of this being liquid or a solid deep frozen coffee concentrate or a dried coffee concentrate, that is, instant coffee, for instance spray-dried or freeze-dried instant coffee powder. More particularly, the invention relates to a method for preparing a coffee concentrate of an improved quality, wherein roasted, ground coffee is subjected to two extractions, the second extraction being carried out at a higher temperature than the first extraction. As stated, the method is suitable for preparing liquid as well as solid concentrates. Still more particularly, the method according to the invention comprises the extraction of coffee wherein, in an initial step, aroma is captured, which aroma, later in the process is added again to the extract to be prepared. The method further provides a new coffee concentrate which forms a further aspect of the present invention. The coffee extracts obtainable according to the present invention are concentrated to form a liquid coffee concentrate and/or instant coffee, in particular instant coffee spray-dried or freeze-dried granules.
As is generally known, and also according to the present invention, coffee extracts are recovered by contacting roasted and ground coffee beans with water or an aqueous solution. On an industrial scale, the intention is to achieve an extraction efficiency which is as high as possible. This means that as many aroma substances, that is odorants and flavourings, as possible are to be extracted from the ground coffee. In the state of the art, aroma substances are recovered from roasted coffee as well as from already extracted, roasted coffee, the latter often through steam stripping.
A known method for preparing a coffee extract is described in European patent application 0 352 842. Herein, a method is described wherein a primary extract is prepared from ground, roasted coffee by exhaustive primary extraction with water or an aqueous solution in one or more extraction cells. The extraction liquid is supplied to one of the extraction cells. Then, a secondary extract is prepared through a secondary extraction with water or an aqueous liquid in one or more extraction cells. From one of these extraction cells, the secondary extract is withdrawn. When a primary extraction cell has been exhaustively extracted, usually at an atmospheric pressure or increased pressure and at a feedwater temperature between 80-100° C., this extraction cell is connected through to the secondary extraction section of the extraction battery, a series-connection of percolators. In this extraction battery, the ground coffee beans are subjected to an extraction at a higher extraction temperature, as a rule at a feedwater temperature between 120-165° C. The first fraction of secondary extract from the secondary extraction is fed to the primary extraction cell as extraction liquid. The remaining extract, the second fraction of secondary extract, obtained from the secondary extraction, is combined with the primary extract.
Before being combined with the secondary extract, the primary extract is subjected to a concentration step in which the aroma components present in the primary extract are recovered by, for instance, steam stripping; these aroma components are recovered so as not to (partially) lose them in the concentration step. Then, the combined extracts are concentrated by evaporating water, after which the recovered aroma components are added to the coffee concentrate.
The object of the present invention is to provide a method with which an improvement of the quality of the coffee concentrate and of the instant coffee can be obtained. In particular, the object of the invention is to prevent the aroma recovery step from at least the primary extract by means of steam stripping. The invention further intends to provide a method which uses less energy and requires less operations and processes. A further object is to prepare a coffee concentrate with which a better tasting and smelling coffee can be prepared.